Development of secretory function in rodent submandibular salivary glands follows a complex pattern of cellular differentiations. One objective of this project is to provide a quantitative description of biochemical syntheses associated with qualitative changes in the secretory cell population during development using cell-type specific markers. A mouse sialomucin presumably from submandibular acinar cells has been electrophoretically purified. This will be characterized by its amino acid and carbohydrate composition. Antiserum produced against this mucin will be used to confirm its cell-type origin by immunofluorescence. The absolute amounts of mucin and its synthesis rates in development will be studied by immunoprecipitation. Proteins specific for other secretory cell types will also be isolated. As an approach to the investigation of the cellular origins of salivary gland secretory cells, parotid cells have been demonstrated to synthesize and secrete alpha-amylase in culture for at least seven weeks. These cells have also been subcultured and shown to continue to produce alpha-amylase. By establishing that the biochemical phenotype of secretory cells is stable during long-term culture, these results provide a rationale for investigating the possibility of developmental multipotency in clones of embryonic and neonatal salivary gland cells in culture.